Traditionally, large computing networks comprised a large number of servers with direct-attached storage. In such networks, disaster recovery can be slow and often only some of the storage capacity of each server is used because the servers can typically not share memory. If one server malfunctions, getting the system back up involves reinstalling the operating system, recovering the data from tapes and transferring the data to the server after the operating system has been reinstalled.
In storage area networks (SANs) the storage elements do not belong to individual servers. Instead, the storage elements are directly attached to the network and storage is allocated to the servers when required. The storage elements may be located remotely off the servers. Therefore, even if the infrastructure containing the servers is destroyed, the data can still be recovered. Moreover, the relocation of the hosts in the network is made easier because the storage elements need not be moved with the hosts. Additionally, the upgrade of the network is easier because the hosts do not have to be upgraded individually in their separate locations. Yet further, if one server malfunctions the downtime of the system is reduced because a new server can quickly be set up and pointed at the relevant storage volumes in the storage elements without the need of recovering the data.
A network of data links including a plurality of switches is required to connect the servers and the storage elements in a SAN. To further reduce the downtime of the network as a result of a failure of one or more of the components, redundant links are often included between the servers and the storage elements such that if one link malfunctions another one can be used and the network can be used without interruptions. To manage the system and ensure that there are enough redundant paths, a management program is often required. The downtime of the system can further be reduced if the management program can analyze faults, assess the state of the network and ensure that the input/output continuity is maintained with optimal performance.
The invention was made in this context.